The present invention relates to a prosthetic acetabular cup inserter and impactor, for use particularly, but not exclusively, in minimal invasive surgery (MIS) with a short incision.
Prosthetic acetabular cup inserter and impactors are used to implant prosthetic acetabular cups into the cavity of a patient's hip, and generally comprise an elongate straight or curved body with a cup engaging head at a first end thereof, and a handle and impaction anvil at a second end thereof. The surgeon releasably fits a cup implant to the cup engaging head, and then positions the cup inside the patient's hip. He then applies a hammering force to the impaction anvil to secure the cup in place, before releasing the cup from the cup engaging head.
In Minimally Invasive Surgery (MIS) it is common to use an inserter and impactor with a curved body, which is shaped to minimise trauma to the patient when it is inserted. In many cases the cups have irregular shapes and/or holes which have to be aligned inside the patient at a particular angle. With such constructions it is important to axially align the cup correctly in relation to the body of the inserter and impactor prior to insertion, so it is properly aligned with the patient's hip when the curved body is inserted as desired.
In U.S. Patent Application Publication No. 2011/0130763 in the name of the applicant, the disclosure of which is incorporated herein by reference, a prosthetic acetabular cup inserter and impactor is disclosed in which the cup engaging means can be axially rotated in relation to the body. In particular, there is a locking means which locks the cup engaging means against axial rotation, which can be released to allow it to be axially rotated in relation to the curved body, and then re-locked when a desired angular position is achieved. Thus, a surgeon can position the cup in relation to the curved body to his liking prior to, or even during, insertion.
However, in this construction the cup engaging means and the body can only be rotated in relation to one another by direct manipulation thereof (or when the cup is held in position inside the acetabulum of the patient). There is shown an operating knob which can rotate a part of the cup engaging means, but this is only for the purposes of engaging and disengaging the cup.
Other devices owned by the assignee or its affiliates of the present invention are U.S. Pat. Nos. 7,341,593, 7,462,180 and 7,993,348, U.S. Patent Application Publication Nos. 2011/0130763 and 2011/0184423.
In U.S. Patent Application Publication No. 2008/0021481, in the name of BURGI, there is disclosed a prosthetic acetabular cup inserter and impactor in which the cup engaging means can be axially rotated in relation to the body by an operating means. The operating means comprises a rigid drive train fitted inside the curved body, which has a rotation handle at one end. The cup is screw threaded to the opposite end of the drive train, and initially the drive train is axially rotated by the handle to facilitate this. However, once this is achieved the surgeon may then axially rotate the handle to orient the cup to a preferred position. The cup is then drawn back onto a head to lock it in position. To release the cup engaging means from the cup after insertion, the handle is axially rotated in the opposite direction to as initially in order to release the screw threaded connection.
However, the device shown in BURGI finds limited application, as it can only be used in instances where a cup is engaged via a screw threaded hole formed in its inner surface. In particular, it cannot function with a cup which is not provided with such a hole, which may be preferred. In addition, some cups are not only engaged by an inserter and impactor at their inner surface, but also by an impaction plate applied to their outer rim. BURGI can only be used to rotate a cup engaging means engaging a cup at its inner surface, and not where a cup is also engaged at its outer rim, as there is no way to also rotate an impaction plate.
In U.S. Pat. No. 7,833,276, assigned to the assignee of the present application there is disclosed a prosthetic acetabular cup comprising an inner part-spherical bearing surface and an outer peripheral rim portion which is shaped to mimic the contours of the natural shape of an acetabulum. The outer peripheral rim portion has an illium rim portion, an ischium rim portion and a pubis rim portion. The portions of the rim between the pubis rim portion and the illium rim portion and between the pubis rim portion and the ischium rim portion are concave and slightly more proximal than the pubis rim portion; the portions of the rim between the illium rim portion and the pubis rim portion, and between the illium rim portion and the ischium rim portion are more concave and proximal than the illium rim portion; and the portions of the rim between the ischium rim portion and the illium rim portion and between the ischium rim portion and the pubis rim portion are more concave and proximal than the ischium rim portion.
This document also discloses a prosthetic acetabular cup inserter and impactor for use with such an acetabular cup, which comprises an annular disc with an annular engagement wall which is shaped to engage the outer peripheral rim of the cup. The annular engagement wall is fixed in relation to the body of the inserter and impactor. With this type of cup and inserter and impactor it is not possible to axially rotate the cup in relation to the engagement wall, as they have irregular shapes. Therefore, axial rotation of the cup in relation to the body in this case is not possible.
In U.S. Patent Application Publication No. 2011/0130763 referred to above, and in U.S. Pat. No. 7,341,593, the disclosures of which are incorporated herein by reference, both assigned to the assignee of the present invention, there are disclosed prosthetic acetabular inserter and impactors which engage the interior surface of the cup by means of a compressible or expandable resilient ring. This is advantageous because no fixing means are required on the interior surface of the cup. However, in U.S. Patent Application Publication No. 2011/0130763 there is no impaction plate, and although there is such a feature in U.S. Pat. No. 7,341,593 there is no relative axial rotation at all in that case.
The present invention is intended to overcome some of the above problems.